Continuous casting plants known in the state of the art for the production of long rolled products have considerable limitations in that, for reasons intrinsically connected to operating constraints and performance of the components, their productivity does not generally exceed 25-40 ton/h.
Consequently, in order to obtain higher productivity it is necessary to increase the number of casting lines connected to the same rolling line, which can be up to 8 lines or more.
This entails, among other things, the need to translate the billets or blooms exiting from the various casting lines on a single entrance point of the heating furnace, with the consequent losses of temperature during the transfers.
As a consequence of this consideration, a considerable quantity of energy is needed to feed the heating furnace, to restore the temperature lost and bring it from the entrance value, comprised between 650° C. and 750° C., to the value suitable for rolling, that is, in a range comprised between 1050° C. and 1200° C.
Moreover, the need to transfer the segments of billets or blooms from the various casting lines to the point where they are introduced into the furnace, imposes limitations on the length and therefore the weight: the length of the billets or blooms is comprised between 12 and 14 meters, up to a maximum of 16 meters, and the weight is on average equal to 2-3 tons.
These process necessities and limitations are the main cause of an increase in energy required for heating the billets or blooms, and of a worsening in achieving the maximum productivity, due both to the large-sized tundishes that are needed to serve several casting lines and also to the large number of billets or blooms to be processed given the same number of tons/hour to be produced, with consequent high number of crops, heads entrances into the stands of the mill and sub-lengths with non-commercial sizes.
To overcome this disadvantage, the number of casting lines has been reduced to two only, which has allowed to provide a suitable temperature maintenance and/or possible heating apparatus which receives the blooms from the two lines and renders them available to the rolling line located downstream.
One purpose of the present invention is therefore to devise a temperature maintenance and/or possible heating apparatus for continuously cast long metal products and a relative method associated with two casting lines which allows to manage in a simple and reliable manner the segments of cast product, sheared to size, without intermediate movements and/or transfers between the casting lines.
Another purpose of the present invention is to exploit to the utmost the enthalpy possessed by the original liquid steel along all the production line, and in particular inside the maintenance and possible heating apparatus, reducing temperature losses in the time between shearing the cast product to size and sending it to the rolling step, so as to obtain a considerable saving of energy and a reduction in the running costs compared to conventional processes.
Further purposes of the invention are:
to allow stoppages of the rolling mill without having to interrupt the casting process upstream, thus obtaining a high plant utilization factor;
to reduce to a minimum or eliminate the scrap material in emergency situations or during programmed stoppages and so completely recover the product which in these situations is temporarily accumulated inside the temperature maintenance and/or possible heating apparatus, thus allowing to obtain a higher yield, equal to the ratio between weight of the finished product and weight of the liquid steel to produce a ton.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.